The present invention relates generally to packaging, and more specifically, to recloseable blister packaging.
2. Description of Prior Art
Use of blister packages is a convenient method for displaying merchandise in retail stores. A typical blister package includes a thermoformed thermoplastic blister formed with a bubble for receiving articles of merchandise, and a back connected to the blister to close the bubble and retain the merchandise in the package.
When used to display a quantity of relatively small articles such as screws, nuts, bolts, fuses, rivets and the like, it is desirable to use a recloseable blister package. This allows the package to serve as a recloseable storage container for the merchandise, as well as to display the merchandise.
One prior method of making a recloseable blister package is to thermoform the front blister and the back closure member from a single sheet of plastic, with an integral hinge formed between the front and back for opening and closing of the package, and with integral interlocking flanges or other complimentary male/female closure arrangements to provide for releasable closure of the package. Examples of such arrangements are shown in Shields, U.S. Pat. No. 4,499,353 and Harding, U.S. Pat. No. 4,512,474. The cost to make tooling for thermoforming plastic parts is, in general, relatively expensive, and as the complexity of the formed part increases, so does the initial tooling costs. Thus, the tooling necessary to form such complicated reclosable blister package arrangements is relatively expensive.
Another common technique for constructing reclosable blister packages is to use a plastic blister with a paperboard or card stock back provided with a reclosable panel. Such an arrangement is desirable because (1) the tooling required to cut the back from a sheet of flat stock is typically less expensive than the tooling necessary to thermoform the back from plastic, and (2) although flat paperboard, card stock and flat plastic may be used interchangeably, paperboard and card stock are typically less expensive than plastic, and product or merchandising information is more easily printed on paperboard or card stock than on plastic. However, a disadvantage of paperboard and card stock is that they tend to be less durable than plastic, and are prone to deformation if bent, or spreading as plies of a multi-ply paperboard tend to separate after repeated opening and closing of the package.
Several reclosable blister packages with paperboard backs are known in the prior art. Unfortunately, many prior package arrangements tend to lose their ability to remain closed, after being opened and closed several times, as a result of deformation or separation of the back in the area of interlocking engagement, as well as suffering from other undesirable characteristics.
Kuchenbecker, U.S. Pat. No. 4,210,246 and U.S. Pat. No. 4,236,636 utilize a blister provided with a plastic tab having ears that must be bent to slip through a cut-out in the paperboard back, and that must engage the back surfaces surrounding the cut-out for interlocking between the blister and the back.
The arrangement of Nertman, U.S. Pat. No. 4,496,052 is especially sensitive to wear, utilizing a plastic blister formed with projections having a shaped profile and circular cross-section to interlock into holes formed in the back.
Yeager, U.S. Pat. No. 5,353,935 teaches use of a plastic blister formed with detents to overlap and retain the paperboard back in the closed position. In this instance, the back becomes increasingly difficult to press into the relatively narrow space between the detents and the back of the blister for closing of the package as the associated edges of the back deform from repeated use.
Dutcher, U.S. Pat. No. 4,209,095 relies on relatively narrow interlocking edges of the paperboard back to effect re-closure of the package. These edges are sheared from the paperboard back when the package is initially opened, and careless or improper initial opening will not generate the desired edges, resulting in loss of the ability to properly re-close the package.
Boyle, U.S. Pat. No. 4,200,193 utilizes a tab formed in the paperboard back for positioning into an overlapping, substantially parallel relationship with an edge of the blister to effect closure of the package. Unfortunately, if this package is oriented with its back facing downwardly, the weight of articles in the blister will cause an "opening" torque on the tab and pivot the tab back over the edge of the blister.
Thus, it is clear that there is a need for a reclosable blister package having an improved, yet relatively simple and cost-effective interlocking arrangement between a thermoformed plastic blister and a paperboard back.